One important area of development in the area of absorbent articles of the above-mentioned type is the control of odourous compounds forming typically after the release of body fluids, especially over a longer period of time. These compounds include fatty acids, ammonia, amines, sulphur-containing compounds and ketones and aldehydes. They are present as natural ingredients of body fluids or result from degradation processes of natural ingredients such as urea, which are frequently assisted by microorganisms occurring in the urogenital flora.
Various approaches exist to suppress the formation of unpleasant odours in absorbent articles. WO 97/46188, WO 97/46190, WO 97/46192, WO 97/46193, WO 97/46195 and WO 97/46196 teach for instance the incorporation of odour inhibiting additives or deodorants such as zeolites and silica. The absorption of bodily liquids reduces however the odour inhibiting capacity of zeolites as soon as these become saturated with water, as mentioned for instance in WO 98/17239.
A second approach involves the addition of lactobacilli with the intention of inhibiting malodour-forming bacteria in the product. The incorporation of lactobacilli and their favourable effect are disclosed for instance in SE 9703669-3, SE 9502588-8, WO 92/13577, SE 9801951-6 and SE 9804390-4.
Another approach is the use of partially neutralized superabsorbent materials (acidic superabsorbent materials) (see WO 98/57677, WO 00/35503 and WO 00/35505).
Therefore, an ongoing demand exists in the art for effective odour-control systems in absorbent articles. In particular, it would be desirable to provide an odour-control system which achieves efficient odour reduction while maintaining the bacterial flora in the urogenital region.
US 2006/0036223 and US 2006/0036222 disclose absorbent articles comprising a bodily exudate modifying agent, a skin care formulation, and a bodily exudate modifying agent neutralizer. The latter may be an enzyme inhibitor which can be selected from a large group of compounds including zinc salts of both saturated and unsaturated monocarboxylic acids. Optionally, the skin care formulation comprises a further ingredient selected from the group comprising amongst many other members preservatives, antimicrobial actives and antifungal actives. US 2006/0036223 and US 2006/0036222 aim at reducing the viscosity of bodily exudates to facilitate absorption of the exudates into the absorbent article. Odour reduction is not an issue.
EP-A-165 074 describes a hydrophilic polymer material, e.g. for the manufacture of sanitary napkins and diapers. The hydrophilic polymer material can be produced by a process during which a specific hydrogel is dried and may be contacted with an aqueous solution. Apart from electrolytes, nutrients, physiologically active polypeptides and proteins, the aqueous solution may also contain antibacterial agents. Moreover, zinc ions may be incorporated into the hydrogel, e.g. in the form of zinc sulphate or a salt of an acidic amino acid. Zinc ions are stated as having a beneficial effect on cell growth. Odour reduction is not addressed in the reference.
The bacteriostatic, bactericidal and antifungal compositions of EP-A-0 366 869 comprise lysozyme, a mineral component and an immunomodulating agent. The mineral component, which is stated as enhancing the mycobactericidal effect of lysozyme, may comprise zinc and/or iodine (Claim 5). Zinc can be provided as zinc sulfate, zinc oxide, zinc gluconate and other salts and compounds of zinc. The immunomodulating agent contained in the composition may be selected from, among many others, benzoic acid.
U.S. Pat. Nos. 5,721,295 and 5,847,031 relate to absorbent polymer compositions comprising an ionic or covalent cross-linking agent. The ionic cross-linking agent may be a metallic compound selected from the group consisting of water-soluble magnesium, calcium, aluminum, zirconium, iron and zinc compounds (cf. Claims 6 and 21 of D8a; and Claims 6 and 19 of D8b). The zinc compounds may be the salts of inorganic acids or carboxylic acids. A huge many of suitable covalent cross-linking agents is mentioned in the reference, amongst those citric acid. U.S. Pat. Nos. 5,721,295 and 5,847,031 further describe an active substance-containing composition comprising the absorbent polymer composition and at least one active substance, which may be selected from the group consisting of drugs, pesticides, bactericides and perfumes. The focus of the references is on biodegradability, and odour reduction is not an issue.
U.S. Pat. No. 6,015,547 relates to a storage clarity-stable aqueous or aqueous/alcoholic solution of zinc ions in the presence of at least one of bicarbonate and carbonate ions. The solution comprises a zinc salt of a first anion. Optionally, the solution may contain antibacterial agents. The gist of the patent is on combining zinc ion containing compounds and bicarbonate and/or carbonate ion containing compounds each of which is in solution, i.e. without liberation of carbon dioxide and without the formation of insoluble basic salts of zinc and carbonate.
The articles for applying a skin care composition to the skin in accordance with U.S. Pat. No. 6,153,209 may comprise a skin care agent which, amongst a large number of compounds, may be zinc acetate. Antibacterial actives are mentioned in a long list of further ingredients. However, the reference does not suggest any effect in terms of odour reduction by using a combination of an organic zinc salt, such as zinc acetate and a preservative.
U.S. Pat. No. 7,005,557; US 2003/0077307 and US 2006/0064068 relate to articles, in particular disposable absorbent articles having a film-forming composition comprising a viscosity enhancing agent, and optionally anti-microbials (selected from a lengthy group). The documents provide a very long list of viscosity enhancing agents including metal ester complexes of aluminum, magnesium, or zinc with stearates, behenates, palmitates or laureates. The object of these documents is not the reduction of odour but the formation of a protective barrier against fluids, body exudates and other irritants.
The highly swellable absorption medium of US 2004/0213892 comprises at least one Lewis acid as a coating agent. A large number of suitable Lewis acids is provided, amongst those benzoic acid, citric acid and water-soluble acetates, formates, oxalates or lactates of inter alia zinc. However, the document fails to disclose a preservative in combination with an organic zinc salt. Moreover, the object of US 2004/0213892 is on a reduced caking tendency in a moist environment and/or at high temperatures, whereas odour reduction is not an issue.
US 2005/0101927 is concerned with moisturizing and lubricating compositions which may be used on absorbent products. The absorbent products comprise an immobilizing agent. Many compounds, including zinc stearate, are stated as being suitable as the immobilizing agent. While the optional addition of preservatives is envisaged, odour reduction is not an issue.
WO 99/00090 relates to a faecal management device which comprises a specific bag comprising a moisture vapour permeable wall material. According to a specific embodiment, the wall material further comprises an odour control agent. Many odour control agents are exemplified, amongst those zinc ricinoleate and, as a different type of odour control agents, antimicrobics such as benzoic and sorbic acid. However, WO 99/00090 fails to disclose a preservative and organic zinc salt in combination for achieving malodour reduction. In particular, the function of zinc ricinoleate as an ammonia absorber is not addressed.
WO 99/30753 is concerned with odour control particles for use in absorbent articles. The odour control particles comprise an effective amount of a liquid activated particle separating means. There are two kinds of these separating means, namely physical and chemical ones. Sodium chloride (NaCl) is given as an example of a physical separating means. Citric acid is exemplified as a chemical separating means. The odour control particles for absorbent particles comprise odour control active materials, amongst those zinc cations. Any other known odour control active is referred to as being likewise suitable for combating malodours. No organic zinc salt is mentioned in WO 99/30753.
DE 10256569 A1 relates to water-absorbing, crosslinked, acid group-containing polymers in the form of mainly open-cell foam comprising at least one odour control agent selected from compounds with an anhydride group, compounds with an acidic group, cyclodextranes, bactericides and surfactants with an HLB value of less than 12. One example of bactericidal compounds are zinc compounds such as zinc chloride. However, no organic zinc salt is mentioned in this reference.
From other technical areas it is further known that organic zinc salts of unsaturated hydroxylated fatty acids such as zinc ricinoleate are deodorizing active ingredients (see for instance DE-A-1792074, DE-A-2548344 and DE-A-3808114).
As will be appreciated from the above, the prior art is not aware of the favorable, in particular synergistic effects of using an antibacterial or alkali metal chloride in combination with an organic zinc salt.
It is one technical object of the present invention to overcome deficiencies discussed above in connection with the prior art.
It is one further technical object to provide an absorbent article having an efficient odour control system.
It is one further technical object of the present invention to considerably reduce or eliminate ammonia formation in absorbent articles.
Further objects will become apparent from the following description of the invention.